在第Ⅲ象限时，象限角R与方位角A的关系为( )。
A．R=180°-A
B．R=180°+A
C．R=A-180°
D．R=A+180°
参考答案：C
Tom _____ a lot of friends since he came to China last year.[ ]
A. made
B. makes
C. is making
D. has made
城市总人口分为基本人口、服务人口和被抚养人口。( )
